1. Field of the Invention
The present invention relates generally to batteries for use in portable devices and, more particularly, to controlling unintended motion of batteries installed in such devices.
2. Related Art
Sudden cardiac arrest, i.e., a heart attack, has been attributed to over 350,000 deaths each year in the United States, making it one of the country's leading medical emergencies. Worldwide, sudden cardiac arrest has been attributed to a much larger number of deaths each year. One of the most common, and life threatening, consequences of a heart attack is the development a cardiac arrhythmia commonly referred to as ventricular fibrillation. When in ventricular fibrillation the heart muscle is unable to pump an sufficient volume of blood to the body and, more importantly, to the brain. Ventricular fibrillation is generally identifiable by the victim's immediate loss of pulse, loss of consciousness and a cessation of breathing. The lack of blood and oxygen to the brain may result in brain damage, paralysis or death to the victim.
The probability of surviving a heart attack or other serious heart arrhythmia depends on the speed with which effective medical treatment is provided. There are four critical components of effective medical treatment that must be administered to a victim of sudden cardiac arrest: (1) early cardiopulmonary resuscitation to keep the blood oxygenated and flowing to the victim's brain and other vital organs; (2) early access to emergency care; (3) early cardiac defibrillation to restore the heart's regular rhythm; and (4) early access to advanced medical care. If prompt cardiopulmonary resuscitation is followed by defibrillation within approximately four minutes of the onset of symptoms, the victim's chances of surviving sudden cardiac arrest can approach or exceed forty percent. Prompt administration of defibrillation within the first critical minutes is considered one of the most important components of emergency medical treatment for preventing death from sudden cardiac arrest.
Cardiac defibrillation is an electric shock that is used to arrest the chaotic cardiac contractions that occur during ventricular fibrillation and to restore a normal cardiac rhythm. To administer this electrical shock to the heart, defibrillator pads are placed on the victim's chest, and an electrical impulse of the proper size and shape that is administered to the victim in the form of an electric shock. While defibrillators have been known for years, they have typically been large and expensive making them unsuitable for use outside of a hospital or medical facility.
More recently however, portable external defibrillators for use by first responders have been developed. A portable defibrillator allows proper medical care to be given to a victim earlier than preceding defibrillators increasing the likelihood of survival. Such portable defibrillators may be brought to or stored in an accessible location at a business, home, aircraft or the like, ready for use by first responders. With recent advances in technology, even a minimally trained individual can operate conventional portable defibrillators to aid a heart attack victim in the critical first few minutes subsequent to onset of sudden cardiac arrest.
Portable defibrillators require an energy source other than an alternating current source to operate in the anticipated environment. Although several manufacturers have provided speciality battery packs for their defibrillation units, typically, such portable defibrillators use a standard, commonly available, rechargeable battery pack, such as those used in video camcorders. Conventional defibrillators use standard mechanical and electrical adapters to mechanically and electrically connect the battery pack to the defibrillator. The use of popular battery packs allows for the easy and inexpensive purchase of replacement batteries when needed. Generally, battery packs may include a sealed lead acid (SLA) battery, a nickel cadmium battery, a lithium battery or the like.
When installed, the electrical connection between the battery contacts and the device must be maintained under the anticipated operational conditions. Portable defibrillators are roughly handled, stored for long periods of time and are subject to all types of shock and vibration depending on where they are stored and the manner in which they are transported to the patient. For example, the electrical connection between the battery terminals and the defibrillator contacts must not be loose or capable of being separated during use. A loose connection between the battery and the defibrillator can decrease battery life or cause the generation of false defibrillator status indications. Such poor connections may also cause improper battery charging or unnecessary maintenance to be performed on the instrument. Micro-motion of the battery pack also may cause arcing, resulting in contact and terminal welding or fretting (that is, pitting and erosion) due to such arcing.
One conventional attempt to circumvent this problem has been to use chemical coatings on the battery contacts to prevent arcing. Drawbacks associated with the use of such coatings has been their high cost and propensity to wear with extended use. This is particularly problematic in defibrillators and other medical support devices that must perform reliably despite being used in environments that subject them to frequent shock and vibration.
Another conventional approach has been to rigidly connect the battery to the instrument. However, battery packs are generally manufactured to high tolerances. As a result, conventional techniques for rigidly attaching the battery pack to the instrument are complex and bulky. Accordingly, such techniques are impractical to manufacture and install in portable devices, particularly portable defibrillators which must provide the operator with the ability to quickly and easily replace the battery.
What is needed, therefore, is an apparatus for ensuring the proper and continuous connection between battery terminals and the instrument contacts so as to prevent arcing. Such an apparatus should not interfere with the operator's ability to replace the battery.